Synthesis, Characterization, and Gas Permeation Properties

Introduction
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Dendronization of Ethyl Cellulose
Dendrimers, a class of precisely branched, highly symmetrical, tree-like
macromolecules capable of furnishing the most exquisitely tailored forms and
functions ever realized outside the realms of nature, have evolved from a little more
than a curiosity into new horizons of macromolecular architecture finding potential
applications in pharmaceutical, biotechnological and polymer sciences and are
expected to reign as the flagship building blocks of nanotechnology. 1 Owing to the
unique architectural and functional control achieved during their synthesis, dendrimers
possess characteristic structural features and properties quite different from those of
their linear counterparts, and have extensively been studied in the past three decades. 2
Despite such an enormous activity enriching the structural diversities of dendrimers,
research has almost exclusively been focused on dendrimers with small cores, except
for a US patent filed by Tomalia and Kirchhoff in 1987, 3 followed by a few reports 4
until a breakthrough in the synthesis of dendronized polymers was reported by
Schlüter in the mid 90s, 5 recognizing the significance of dendron functionalization for
the backbone conformation and the overall shape of the resulting macromolecules.
Dendronized polymers are characterized by the presence of dendritic
fragments attached to a polymeric backbone and the past few years have witnessed a
variety of dendritic substituents and polymeric backbones to which they are appended
to. 6 Recently, there is an increasing interest to exploit the dendritic macromolecules
or dendron appendages for the chemical and surface modification of silica, 7 agarose, 8
carbon, 9 chitosan, 10 and DNA; 11 however, the reports concerning the dendronization of
cellulose or its organosoluble derivatives are few and far between. 12
Cellulose, an inexhaustible natural polymeric material endowed with a
polyfunctional macromolecular structure and an environmentally benign nature,
suffers from the lack of solubility in most organic solvents emanating from its
supramolecular architecture. However, ethyl cellulose, an organosoluble cellulosic,
possesses the fascinating features of extensive linearity, chain stiffness, excellent
durability, chemical resistance, mechanical strength, hydrophobicity, non-toxicity, low